1. Field of the Invention
This invention relates generally to readers for optically encoded data, and, more particularly, to a system for recognizing information carried in the form of raised surface areas on an information carrying member, such as an embossed credit card.
2. Description of the Prior Art
Numerous systems have been devised for detecting and interpreting data optically encoded on a record medium. For example, it is now quite common to have the bar code affixed to an article of merchandise read at a checkout counter simply by passing an optical wand over the code area, and processing the output data in an associated computer. Such decoding is simplified by the fact that the bar code is essentially one dimensional, i.e., the information is extracted by scanning a single line or track along which the data is formed.
Where embossed or raised characters are to be optically decoded, a second dimension is added, since the various characters, numerals, for example, must be scanned both along the length of the data track as well as in the width direction transverse to the track. Accordingly, a plurality of detectors are typically positioned transverse to the track, with such detectors operating in parallel as the reader is passed over the record medium. Since the areas to be scanned are closely spaced, radiant or light energy from one or more sources or emitters may be directed to the record medium via light pipes or fiber optics. Similarly, light or radiant energy reflected by the characters on the record medium can be directed to an array of detector elements by additional light transmitting fibers. Examples of such readers are contained in U.S. Pat. Nos. 3,786,238 to Heisner and 3,706,874 to Lockard.
While the aforementioned arrangements may operate satisfactorily in certain applications, the use of fiber optics is disadvantageous by virtue of the cost and complexity associated with the construction and precise alignment of a plurality of fiber tubes. Also, since light fibers must generally be fabricated so as to exhibit total internal reflection, whereby energy from one fiber cannot interact with energy from another, common termination in a single detector element presents difficulties in construction, and duplication of components results. Still further, light pipes are typically terminated in a smooth surface normal to the fiber; these surfaces emit and receive radiant energy over a large solid angle, rather than being focused at a small, well defined area. Hence, it becomes quite difficult to obtain the spatial resolution needed to satisfactorily distinguish between the signals generated by various portions of the characters being read.
In view of the foregoing, it is the broad object of the present invention to reduce the cost and complexity of readers for optically encoded data, particularly of the raised or embossed type. Specific objects are to avoid the need for fiber optics in a reader of the type described, to reduce to one the number of detector elements needed to scan an embossed character, and to improve the reader resolution and sensitivity by focusing radiant energy at discrete points on a line transverse to the data track and similarly focusing energy reflected from the aforesaid points on the detector.
As will be discussed in further detail hereinafter, a still further object of the present invention is to improve discrimination of signals received from the detector with a threshold circuit which is simple yet sensitive. In this way, the often complicated and cumbersome circuits of the prior art are avoided, and successful reading may be accomplished despite the fact that the embossments may have become distorted or flattened by user neglect.